Boosting selective C2H2/CH4, C2H4/CH4 and CO2/CH4 adsorption performance via 1,2,3-triazole functionalized triazine-based porous organic polymers

Nitrogen-rich porous organic polymers have shown great potentials in gas adsorption/separation, photocatalysis, electrochemistry, sensing and so on. Herein, 1,2,3-triazole functionalized triazine-based porous organic polymers (TT-POPs) have been synthesized by the copper-catalyzed azide-alkyne cycloaddition (Cu-AAC) polymerization reactions of 1,3,5-tris(4-azidophenyl)-triazine with 1,4-diacetylene benzene and 1,3,5-triacetylenebenzene, respectively. The characterizations of N₂ adsorption at 77 K show TT-POPs possess permanent porosity with BET surface areas of 666 m²·g^-1 (TT-POP-1) and 406 m²·g^-1 (TT-POP-2). The adsorption capacities of TT-POPs for CO₂, CH₄, C₂H₂ and C₂H₄, as well as the selective separation abilities of CO₂/N₂, CO₂/CH₄, C₂H₂/CH₄ and C₂H₄/CH₄ were evaluated. The gas selective separation ratio of TT-POPs was calculated by the ideal adsorbed solution theory (IAST) method, wherein the selective separation ratios of C₂H₂/CH₄ and C₂H₄/CH₄ of TT-POP-2 was 48.4 and 13.6 (298 K, 0.1 MPa), which is comparable to other adsorbents (5.6-120.6 for C₂H₂/CH₄, 10-26 for C₂H₄/CH₄). This work shows that the 1,2,3-triazole functionalized triazine-based porous organic polymer has a good application prospect in natural gas purification.     

C2H6/C3H8影响CH4爆炸极限参数及动力学特性研究

为研究C₂H₆/C₃H₈对甲烷爆炸极限参数及动力学特性的影响,采用标准的可燃气体爆炸极限测定装置测定了不同配比的C₂H₆/C₃H₈混合气体对甲烷爆炸极限的影响规律,同时得出了氮气惰化条件下甲烷爆炸临界参数的变化规律。此外,利用Chemkin软件模拟了C₂H₆/C₃H₈混合气体对甲烷爆炸过程中中间产物浓度的影响情况,并进行了敏感性分析。结果表明,C₂H₆/C₃H₈的存在降低了甲烷的爆炸上下限,增大了甲烷的爆炸危险度;在氮气惰化过程中甲烷的爆炸上限下降,爆炸下限上升,最终爆炸上下限重合,重合点处甲烷浓度和氮气临界浓度均随C₂H₆/C₃H₈的添加而逐渐减小;此外,C₂H₆/C₃H₈混合气体使甲烷爆炸过程中CO和·H的生成量逐渐增大,而CO₂、·O和·OH的生成量则有下降趋势,通过对爆炸过程中甲烷体积的敏感性分析,发现C₂H₆/C₃H₈的存在在某种程度上促进了甲烷爆炸。对比不同配比的C₂H₆/C₃H₈混合气体,发现C₃H₈含量越高,其对甲烷爆炸过程中相关参数的影响越大,这可为工矿企业的安全生产提供一定的理论依据。     

SCR of NOx with CH3OH on H-mordenite: mechanism and reaction intermediates

The selective reduction of NO_x over H-mordenite (H-m) was studied using CH₃OH as reducing agent. Results are compared with those obtained with other conventional reducing agents (ethylene and methane), with gas-phase reactions, and with other metal-exchanged mordenites (Cu-mordenite (Cu-m) and Co-mordenite (Co-m)). H-m was found to be an effective catalyst for the SCR of NO_x with CH₃OH. When different reducing agents were compared over H-m, CH₃OH > C₂H₄ > CH₄ was the order according to the maximum NO conversion obtained using 1% of oxygen in the feed. Instead, if selectivity is considered, the order results CH₄ > CH₃OH > C₂H₄. In reaction experiments, two distinct zones defined by two maxima with NO to N₂ conversion are obtained at two different temperatures. A correlation exists between the said zones and the CO : CO₂ ratio. At low temperatures, CO prevails whereas at high temperatures CO₂ prevails. These results indicate that there exist different reaction intermediates. Evidence from reaction experiments, FTIR results, and transient experiments suggest that the reaction mechanism involves formaldehyde and dimethyl ether (DME) as intermediates in the 200–500°C temperature range. The surface interaction between CH₃OH (or its decomposition products) and NO is negligible if compared with NO₂, indicating that the oxidation of NO to NO₂ on acid sites is a fundamental path in this system. Different from other non-oxygenated reductants (methane and ethylene), a gas-phase NO_x initiation effect on hydrocarbon combustion was not observed.     

A pillared-layer metal-organic framework for efficient separation of C3H8/C2H6/CH4 in natural gas

Metal-organic frameworks (MOFs) have great potentials as adsorbents for natural gas purification. However, the trade-off between selectivity and adsorption capacity remains a challenge. Herein, we report a pillared-layer metal-organic framework Ni(HBTC)(bipy) for efficiently separating the C₃H₈/C₂H₆/CH₄ mixture. The experimental results show that the adsorption capacity of C₃H₈ and C₂H₆ on Ni(HBTC)(bipy) are as high as 6.18 and 5.85 mmol·g^-1, while only 0.93 mmol·g^-1 for CH₄ at 298 K and 100 kPa. Especially, the adsorption capacity of C₃H₈ at 5 kPa can reach an unprecedented 4.52 mmol·g^-1 and for C₂H₆ it is 1.48 mmol·g^-1 at 10 kPa. The ideal adsorbed solution theory predicted C₃H₈/CH₄ selectivity is as high as 1857.0, superior to most of the reported materials. Breakthrough experiment results indicated that material could completely separate the C₃H₈/C₂H₆/CH₄ mixture. Therefore, Ni(HBTC)(bipy) is a promising material for separation of natural gas.     

CH4/C2H6/C3H8在MOF-505@5GO上吸附相平衡和选择性

应用溶剂热法合成了不同氧化石墨烯（GO）负载量的MOF-505@GO复合材料,分别采用全自动表面积吸附仪、P-XRD、SEM和Raman对材料进行了性能表征,测定了CH₄、C₂H₆和C₃H₈在MOF-505@GO上的吸附等温线,并进行Langmuir-Freundlich方程拟合,依据IAST理论模型计算了C₂H₆/CH₄和C₃H₈/CH₄二元混合气在MOF-505@5GO上的吸附选择性。研究结果表明,随着GO负载量增大,MOF-505@GO复合材料的孔容及BET比表面积先增大后减小,当GO负载量为5%（质量）时,复合材料MOF-505@5GO的孔容及BET比表面积达到最大,当GO负载量进一步增大至8%（质量）和10%（质量）时,复合材料的孔容及BET比表面积逐渐降低。在0.1 MPa和298 K条件下,MOF-505@5GO对CH₄、C₂H₆和C₃H₈的吸附容量分别为0.88、4.81和5.17 mmol·g^-1,相比MOF-505分别提高了14.9%、30.7%和13.1%。MOF-505@5GO对C₂H₆/CH₄和C₃H₈/CH₄的吸附选择性分别为40.1和3056.1,其对C₂H₆/CH₄和C₃H₈/CH₄具有极高的吸附选择性。     

Synthesis of C2H4 by partial oxidation of CH4 over LiCl/NiO

Alkali halide added transition metal oxides produced ethylene selectively in oxidative coupling of methane. The role of alkali halides has been investigated for LiCl-added NiO (LiCl/NiO). In the absence of LiCl the reaction over NiO produced only carbon oxides (CO₂ + CO). However, addition of LiCl drastically improved the yield of C₂ compounds (C₂H₆ + C₂H₄). One of the roles of LiCl is to inhibit the catalytic activity of the host NiO for deep oxidation of CH₄. The reaction catalyzed by the LiCl/NiO proceeds stepwise from CH₄ to C₂H₄ through C₂H₆ (2CH₄ → C₂H₆ → C₂H₄). The study on the oxidation of C₂H₆ over the LiCl/NiO showed that the oxidative dehydrogenation of C₂H₆ to C₂H₄ occurs very selectively, which is the main reason why partial oxidation of CH₄ over LiCl/NiO gives C₂H₄ quite selectively. The other role of LiCl is to prevent the host oxide (NiO) from being reduced by CH₄. The catalyst model under working conditions was suggested to be the NiO covered with molten LiCl. XPS studies suggested that the catalytically active species on the LiCl/NiO is a surface compound oxide which has higher valent nickel cations (Ni^(2+δ)+ or Ni³⁺). The catalyst was deactivated at the temperatures>973 K due to vaporization of LiCl and consumption of chlorine during reaction. The kinetic and CH₄---CD₄ exchange studies suggested that the rate-determining step of the reaction is the abstraction of H from the vibrationally excited methane by the molecular oxygen adsorbed on the surface compound oxide.     

Structural and Optical Properties of Barium Strontium Titanate (Ba0.5Sr0.5TiO3) Thin Films

Ferroelectric Barium Strontium Titanate (Ba_0.5Sr_0.5TiO₃) or BST thin films on quartz substrates have been prepared by using a modified sol gel processing technique. The starting materials are Barium 2-ethylhexanoate Ba[CH₃(CH₂)₃CH(C₂H₅)CO₂]_2, Strontium 2-ethylhexanoate Sr[CH₃(CH₂)₃CH(C₂H₅)CO₂]₂ and Titanium(IV) isopropoxide [TiOCH(CH₃)₂]₄. The precursors except [TiOCH(CH₃)₂]₄ were synthesized in the laboratory. Transparent and crack-free films were fabricated on quartz substrates by spin coating. The as-fired films were found to be amorphous, which crystallized to cubic phase after annealing at 550°C in air for 1 hr. In this paper we report the structural and optical properties of BST films prepared by the modified sol-gel process.

Communicated by Prof. E. C. Subbarao     

Silicone/non-silicone grafted blend composite membranes for air/vapor separation

Four types of new silicon-based graft blended polymers were developed and drawn to thin film composite membranes on high flux microporous polyetherimide support. The membranes and a 1 μm PDMS membrane as a standard were tested for the flux of the gases N₂, O₂, Ar, CH₄, CO₂, CH₃Cl, C₂H₅Cl, C₂H₆, and n-C₄H₁₀ and the vapors methanol (MeOH), t-butyl methyl ether (MTBE), 1, 1, 1-trichloroethane (Cl₃Eth), 1, 1, 2-trichlorofluoroethane (Cl₃F₃Eth), and n-hexane (n-C₆H₁₄). Methanol/argon mixtures were used to check the validity of the calculated selectivities. The results show higher performance for the newly developed membranes.     

Reaction mechanism of methane activation using non-equilibrium pulsed discharge at room temperature

The reaction mechanism of methane activation using non-equilibrium pulsed discharge was largely clarified from the emission spectroscopic study and experiments with higher hydrocarbons and some kinds of isotopes. The strong emission of atomic carbon and C₂ swan band system was observed as well as H Balmer series emission. This indicates that methane was highly dissociated into C and H by electron impact, which is consistent with the result of high C₂D₂ composition in produced acetylene when the mixture of CH₄ and D₂ was fed into discharge region. High electron energy contributed to produce atomic carbon directly from methane, and high electron density promoted the dehydrogenation from CH₃, CH₂ and CH to produce atomic carbon consecutively. The reason for the high selectivity to C₂H₂ was the high concentration of CH or C₂ formed from atomic carbon, and the repetition mechanism of decomposition and recombination among C, CH, C₂ and C₂H₂.     

Comparison between methane and propylene as reducing agents in the SCR of NO over Pd supported on tungstated zirconia

It is now well known that when Pd is supported on acidic supports, it becomes highly selective for the reduction of NO by methane in the presence of excess oxygen. It is also known that this promoting effect not only occurs with acidic zeolite supports, but also with acidic zirconia supports, such as sulfated zirconia (SZ) and tungstated zirconias (WZ). However, this promoting effect has not been investigated for the SCR with other hydrocarbons as reducing agents. In this contribution, we have investigated the behavior of a series of Pd/WZ catalysts and compared them using methane and propylene as reducing agents. The results show some important differences when the reducing agent is changed. For example, while with CH₄ the addition of W to the catalyst results in an increase in both NO and hydrocarbon conversion, with C₃H₆ it results in a decrease in activity. At the same time, while the presence of NO accelerates the activation of CH₄, it inhibits the activation of C₃H₆, moving its light-off to higher temperatures. Finally, an important difference between CH₄ and C₃H₆ as reducing agents is regarding the selectivity towards N₂ as opposed to N₂O. Using CH₄ resulted in much lower production of N₂O than using C₃H₆, over the entire temperature range investigated.     

离子液体[BMIM][DBP]+水+甲醇/乙醇三元工质溶液蒸汽压的测量和预测(英文)

The ionic liquid, 1-butyl-3-methylimidazolium dibutylphosphate ([BMIM][DBP]) was prepared and the vapor pressures of three set of binary solutions H2O(1)/CH3OH(1)/C2H5OH(1) + [BMIM][DBP](2) were measured at different temperature and in the ILs mole fraction range from 0.1 to 0.6 with a static equilibrium apparatus. The measured vapor pressures were correlated with Non-Random Two Liquid (NRTL) activity coefficient model and the average relative deviations (ARD) between experimental and correlated vapor pressures for these binary solutions were 3.19%, 2.42% and 2.95%, respectively. Then, the vapor pressures of two set of ternary solutions H2O(1) + CH3OH(2)/C2H5OH(2) + [BMIM][DBP](3) were measured with an inclined boiling apparatus and further predicted with NRTL activity coefficient model based on the binary interaction parameters coming from fitting the vapor pressures of the binary solutions. The results indicated that the ternary solutions containing [BMIM][DBP] were shown a strong negative deviation from Raoult’s Law when the mole fraction of [BMIM][DBP] was larger than 0.2, which meant that ternary solutions could absorb the refrigerant vapors at the same or below solution temperature. Meanwhile, the average relative deviations between experimental and predicted vapor pressures for ternary solutions were 2.92% and 3.06%, respectively. Consequently, the NRTL active coefficient model used for non-electrolyte solutions was still valid for predicting vapor-liquid equilibrium of binary or ternary solutions containing ILs.     

Non-oxidative reaction of CBrF3 with methane over NiZSM-5 and HZSM-5

Catalytic hydrodehalogenation of CBrF₃ with methane was studied over NiZSM-5 and HZSM-5 in tubular reactor between 573 and 873 K and at ambient pressure. It was found that the incorporation of nickel into HZSM-5 significantly enhanced the activity of the zeolite. A variety of products were formed during reaction, including CH₃Br, CHF₃, CH₂Br₂, C₂F₆, C₂H₄, C₂H₂, C₂H₂F₂, CHBrF₂, CH₂BrF, and C₂H₃Br. XRD analysis showed that these two zeolite catalysts did not suffer any loss in their crystallinity during use. Deactivation of both NiZSM-5 and HZSM-5 may, in part, be due to poisoning of the zeolite by halogens. Coking is another cause of the deactivation of HZSM-5, but appears to play a minor role in NiZSM-5 deactivation. A series of methylated silicone oils was detected during reaction over NiZSM-5.     

Measurement and Prediction of Vapor Pressure for H2O+CH3OH/C2H5OH+[BMIM][DBP] Ternary Working Fluids

The ionic liquid, 1-butyl-3-methylimidazolium dibutylphosphate ([BMIM][DBP]) was prepared and the vapor pressures of three set of binary solutions H2O(1)/CH3OH(1)/C2H5OH(1)+[BMIM][DBP](2) were measured...     

Phase transitions in R2 SnCl6-type crystals (R = NH3 C2H3, NH3C2H5 and N(CH3)4)

The thermal dilatation in (NH₃ ·CH₃) SnCl₆, (NH₃ · C₂H₅) SnCl₆ and [N(CH₃)] SnCl₆ was measured, and as the results it has turned out that (NH₃ ⁶·C₂H₅) SnCl₆ and [N(CH₃)₄]₂ SnCl₆ undergo the first order transitions at 128 K and 158 K, respectively. The low temperature phases of (NH · C₂H₅) SnCl₆ and [N(CH₃)₄]₂ SnC1₆ are found to be monoclinic and tetragonal, respectively, No phase transition was observed in (NH₃ ·CH₃)₂ SnCl₆ down to 77 K.     

TiO2基催化剂还原CO2研究进展

能源危机和环境污染是当今世界发展面临的两大挑战,如何有效缓解煤、石油等不可再生化石资源过度消耗所引发的能源危机,以及由此造成CO₂过量排放引起的温室效应问题,是当前人类发展亟待解决的重大科学问题之一。基于此,本文综述了近年来以TiO₂为光催化剂,以绿色、清洁的太阳光能催化还原CO₂成低价态含碳燃料(如CH₄、CH₃OH、HCHO、HCOOH、C₂H₅OH等)研究进展。在TiO₂光还原CO₂机理基础上,对元素掺杂、半导体复合与染料敏化、高活性晶面调控、低维纳米结构设计、助催化剂、Z型结构设计和单原子催化等方法来提高光还原CO₂反应效率和选择性进行分析,并指出目前研究存在的关键问题和未来CO₂光还原的发展方向。     

条浒苔与稻壳共热解协同效应

为了进一步探究大型海藻与陆生生物质共热解的协同效应,选取条浒苔与稻壳生物质作为代表进行了单样以及不同混合比例的共热解台架试验。通过三相产物产率的计算,以及生物油产物的GC-MS、FT-IR、热值分析和对气相产物的GC分析,研究了条浒苔与稻壳共热解协同效应的影响。共热解的气相产物产率在各个混合比例下均高于理论值,说明共热解对气相产物的生成具有促进作用,同时共热解气相产物中甲烷、乙烷、乙烯、丙烷为主的小分子烃类物质产率高于理论值,生物油中以乙酸为代表的小分子产物明显增多,分析认为条浒苔灰分中Na、K等碱金属具有促进大分子产物进一步裂解的催化作用,进一步验证了条浒苔与稻壳共热解的协同效应。     

Partial oxidation of light alkanes by NOx in the gas phase

Partial oxidations of CH₄, C₂H₆, C₃H₈, and iso-C₄H₁₀ with O₂ were promoted by addition of NO in the gas phase. The addition of NO increased the conversion rate of alkanes and decreased the initiation temperatures for the reactions. Moreover, selectivities and yields to oxygenates, aldehydes, ketones and alcohols, were remarkably improved by the addition of NO. The maxima of one-pass yields of oxygenates were 7% for CH₄, 11% for C₂H₆, 13% for C₃H₈, and 29% for iso-C₄H₁₀. It is suggested that NO₂ produced from NO and O₂ is the initiator for the oxidation of light alkanes. Alkyl nitrite was proposed as the reaction intermediate for the formation of oxygenates. The alkyl nitrite decomposes into oxygenates and NO that works as catalyst for the activation of O₂ and the oxidation of alkanes.     

The homogeneous gas phase oxidation of methane and the retarding effect of basic/inert surfaces

The homogeneous gas phase O₂-based oxidation of methane was studied in the temperature range, from 500°C to 750°C at methane partial pressures ranging from 3 bar to 40 bar. At the lower end of the temperature range methanol, formaldehyde, and CO represent the main products, while at temperatures exceeding 650° C/C-coupled products, C₂H₆, C₂H₄, C₃H₆ and C₃H₈ predominate. The change in selectivity as function of the temperature is well explained based on a free radical chain mechanism with degenerate branching, initiated by the gas phase reaction, CH₄+O₂→CH^·₃+HO^·₂. Bringing in basic catalysts known to catalyze the system at low methane partial pressures, in the reactor e.g. SrCO₃, BaCO₃, and 7% Li/MgO resulted in reduced rates of methane and oxygen conversions, and only minor changes in the selectivity to coupled products were observed.     

The partial oxidation of ethane to acetaldehyde

The mixed oxide (B---P---O) prepared from H₃BO₃ and P₂O₅ was modified to a selective catalyst (B---P---O(S)) to the formation of CH₃CHO after prolonged treatment in a gas mixture of reactants. The contribution of gas-phase chain reactionsto the catalytic oxidations of C₂H₆ on the B---P---O(S) could be neglected. The catalytic active species on the B---P---O(S) was suggested to be a highly dispersed boron oxide supported on BPO₄ crystals. The mixed oxide prepared from BPO₄, H₃BO₃(7atom%), and P₂O₅(3atom%) showed the highest yield of CH₃CHO.     

基于分子动力学模拟的轮胎橡胶气相热解产物反应机理

运用分子动力学的方法,对轮胎橡胶的热解过程进行了模拟,并结合模拟结果和密度泛函数对其气相产物的反应路径进行推测计算。模拟结果表明,热解过程主要分为两个阶段,低温热解阶段发生的主要反应是橡胶长链断裂形成单体,主要产物为异戊二烯、苯乙烯和1,3-丁二烯;高温热解阶段发生的主要反应是单体进一步生成小分子气体,产物中CH₄、H₂、C₂H₄占大部分,还有少量C₂H₆、C₃H₆。其中CH₃·攻击异戊二烯和苯乙烯单体夺取特定位置的H·是生成CH₄的最优路径,H·攻击苯乙烯单体夺取特定位置的H·是生成H₂的最优路径,CH₂CH·攻击1,3-丁二烯单体夺取特定位置的H·是生成CH₂CH₂的最优路径。本文还将热解产物分别跟天然橡胶单独热解和天然橡胶与丁苯橡胶共热解的热解产物做对比,为废旧轮胎橡胶热解得到特定的气相产物和催化热解提供理论依据。